The overall goals of this research project are to study the cellular requirements for the initiation and maintenance of tolerance in mice to a thymic dependent antigen - Human gamma-globulin. In addition we wish to extend our observation that tolerance to HCG in mice can be induced in normal cell populations by cells from tolerant animals and to establish the site of action and mechanisms of such infectious tolerance or active suppression. BIBLIOGRAPHIC REFERENCES: Baird, L.G. and Kaplan, A.M.: Macrophage mediated inhibition of lymphocyte blastogenesis. In Leukocyte Membrane Determinants Regulating Immune Reactivity. V.P. Eijsvoogel, D. Roos and W.P. Zeijlemaker, Eds. Academic Press, New York, l976, p. 361.